Multiple key switch



Nov. 16, 1937.

L. HAMMOND MULTIPLE KEY SWITCH Filed April 24, 1936 5 sheets-sheet 1 @dat WW y

MULTIPLE KEY SWITCH Filed April 24, 1956 3 Sheets-Sheet 2 Z@ /z 25 @d NOV. 16, 1937. L HAMMOND 2,099,204

MULTIPLE KEY SWITCH @attentati New. lr6, 'w37 ia; STATES ATENE esta 19 Glaims.

My invention relates generaily to multiple key switches, and more particulariy to switches usable in electrical musical instruments.

It is an object of my invention to provide an e improved multiple key switch which is simple and durable in construction, which may be easily assembled, and in which the contact points may be easily cleaned.

A further object of my invention is to provide a multiple switch assembly in which all of the parts are contained in a dust-proof housing.

A further object is to provide an improved method of wiring the terminals of the switches to soldering lugs.

A further object is to provide an improved multiple s witch construction in which the individual contact carrying arms may be assembled in their supports without the use of tools of any kind.

A further object is to provide an improved switch contact for switches carrying currents of low voltage and amperage.

A further object is to provide an improved means for actuating multiple switches.

Other objects will'appear from the following description, reference being had to the accompanying drawings, in which:

Fig. 1 is a vertical cross-sectional view of the manual and key-operated switch assembly of an electric organ; l

Fig. 2 is an enlarged fragmentary section taken on the line 2 2 of Fig. l, one of the multiple key switches being shown in closed position;

Fig. 3 is a greatly enlarged fragmentary sectional view taken on the line 3 3 of Fig` 2;

Fig. 4 is in part a plan view of the manual and switch assembly, and in part a sectional view taken on the line 4 4 of Fig. 1;

Fig. 5 is a vertical sectional view taken on the 4o line 5 5 of Fig. 4 and showing the mechanism for shifting the bus bars;

Fig. 6 is a sectional view taken on the line 6 6 of Figs. 1 and 5;

Fig. 7 is a detail illustrating the method of securing the contact arms or switch ilngers in their mounting plates; and

Fig. 8 is a fragmentary vertical sectional view taken onl the line 8 8 of Fig. 4.

vention forms a part of the electrical Amusical instrument which is fully disclosed in my Patent No. 1,956,350, granted April 24, 1934, to which reference may be had for a-disclosureof the general construction of the instrumentA and of the The key switch assembly of the present in- (Cl. SQL-337) various parts used with, but not directly conce1-ned with7 the invention claimed herein.

As more fully disclosed in the aforesaid patent, alternating sine wave currents of the various frequencies of the tempered musical scale are lpro- 5 duced by minute generators, and by means of key-operated switches, current from selected ones of Athese generators, corresponding to the fundamental and the various desired harmonics, are, upon the depression of a key, simultaneouslyin- 10 troduced into the output circuit of the instrument. Inasmuch as the instrument may have sixty-one keys for each manual, and each ,key will operate nine switches, it will be apparent that several hundreds of switches must be provided. These switches are preferably arranged in iles spaced apart by the distance between the successive keys of the standard organ manual, in order that the actuation oi' the switches by the keys may be readily accomplished. For this reason, the usual contact switch construction would notbesuitable for use in an instrument of this character. Furthermore, due to the great number of switches present in the instrument, each switch is very simple and cheap so that the instrument may be produced at a reasonable cost.

Another desirable feature of the switches which is incorporated in the present invention is that the contacts of the switches are made of non-corrosive, non-oxidizing, non-pitting con- 3o ductors. The usual cheaper contact metals are unsuitable because they do not maintain a good contact surface over extended periods of time, and it has been found that some of the rare metals, such as platinum, platinum iridium alloys, and palladium, 'form the most durable and efficient contacts for this type of circuit. In the present invention, due to the novel form of the contacts, the quantity of the rare and expensive contact metal necessary is reduced to a 40 practical value so that even though there are hundreds of switches in the instrument, the cost of the rare metal necessary for over a thousand switch contacts is not excessive.

One oi' the diiilculties formerly experienced 45 with switches of the type usable in electrical musical instruments was that particles of dust or other foreign matter settled between the contacts of a switch and rendered the switch ineiective. Even a small particle of lint or dust located between the switch contacts will inter rupt the circuit because of the extremely low voltage and amperage of the current transmitted through the switch. One of the features of the Present invention is therefore the enclosure of the recess t@ formed in the platesltl. The top sheet vswitching mechanism in a substantially dustproof compartment and the' provision of means for simultaneously wiping or cleaning a plurality or all or the switch contacts. Even though the switch contacts carry currents of low voltage and amperage; and thus the possibility oi damage oi the contact points by arcing vis not present, there ismechanical wear u'pon the contacts, and the construction of the present invention therefore provides means for easily renewing the contact points without disassembling the switch unit.

Referring to Fig.. l, the key switches are enclosed in a dust-proof compartment'composed of a sheet metal L-s'haped strip it', a back plate it, a bottom sheet Ml, and a top sheet it. The i switch assembly is supported by a plurality ofvertical compartment walls it, the. front of each of the compartments-iormedbetween the plates it being enclosed by a exible wall til. `lllhe rear wall l2. is secured to the Lshaped strip. iii by cap screws di, `Vertical plates it have upwardly extending lugs 22 which project into complementary openings formed in the horizontal leg of the Lshaped strip or angle plate it, and have downwardly extending lugs dit near their forward ends which project intoapertures formed in the long strip 3d which overlies the tops of the :tor'

ward ends of the vertical plates it, resting in a i@ is secured to the vertical plates it by cap screws 3d which are threaded in a strip-fi@ extending thev full length of the manual and projecting through apertures it? formed in the plates. The rearward edge of the top sheet is bent upwardly as indicated at it and cornpresses a feltstrip it against the lower i'ace of the forward edge of the angle strip it, thus pre` venting the admission of dust at the joint between the sheet it and angle strip it." The bottom sheet id isseeured to the vertical frame -plates it by cap screws #Stand it which are, threaded in strips t2 and 5ft respectively, these strips projectf ing through. apertures 5d and td respectively formed in the vertical plates it. The space be'-v twee'n the'rearward edge of the lower sheet it and the rear sheet t@ is sealed by a felt strip tt,

and similar felt strips tt and td seal the upper and lower edges respectively oi' the iront compartment walls it. 'These walls have forwardly' extending, flanges tt at their-ends, lsaid anges containing perforations tt.- .As best shown in Fig. i, wires id extending the full length ofA the manual are threaded through the periorations tt and complementary perforations formed in the vertical plates' it, and thus hold the walls tti in position. A

In addition to being properly spaced by the lugs 22 and 2t, the vertical plates it are spaced by strips i12, "it, and lift. These strips are each provided with notches 'il in one edgether-eci, thenotches being oi' sumcient width to receive the plates it. After sliding the strips "i2, lid, and 'it through the complementary shaped apertures formed therefor in the vertical plates iii, the strips are moved laterally'to bring their notches .intopintermeshing engagement with the. plates,

and the strips heid in this'pcsition by pairs of wires 18. It will thus'be apparent that thevertical'plates it are held in properly spaced relation at a plurality of points so that even though the casing for the' switches is subjected to a load and deformed to some extent, the proper spacing of the-plates it will not be disturbed. The assembly as a whole is thusvery exible without sacrificing. accuracy in the alignment of the various parts.

A plurality of switch mounting plates t@ and t2 made of. suitablel insulating material, such as a phenol condensation product, are supported by the vertical plates it. These plates il@ and t2 may be of convenient length, extending approximately the distance between four adjacent vertical plates it. The lower edge of the insulating plate til and the upper edge ofthe corresponding plate t2 are provided with notches of width to receive the vertical plates it, and these notches are interengaged with the vertical plates it by moving the insulating plate tt downwardly and the insulating plate lit upwardly and then inintheir displaced position in locking engagement with the vertical plates it.

As shown in Fig. 8, the insulating plate llt (which is substantially identical in construction;

with the plate' di)4 is provided with a plurality of polygonal apertures tt. The contact arms or switch fingers t@ project through these apertures td and are held in position by the rear plate t2," 'as best shown in Figs. d and 7. The switch ngers @t are preferably stamped from a thin sheet vof phcsphorbronze, and at their rearward ends are provided with an open end slot @t thus. forming a latch portion 96 and a connection portion @8.

As indicated in Fig. 7, the switch fingers' tu are .inserted through the apertures di! in the insulatforward 4ends of the switch dngers @t have va narrow tip idd, tothe lower surface cf which is welded a,y short length oi wire tilt which is preterably marient a palladium alloy, but may be made of platinum, a platinum iridium alloy, or similar vnon-corrosive, non-oxidizing metal. The wire is preferably, for the sake of economy, of ex,-

' tremely small diameter, in the order of .007" in diameter. It is found that a. contact made of this wire will be effective to maire a Igood connection throughout theuseful lii'e of the instrument.

The switch fingers are normally slightly bowed', as indicated in Fig. l, with their forward tips itt abutting against insulating strips tdt which .5er-

tend the full length oi the manual, and are-Y threaded through suitable apertures vformed in insulating bus bar supports lit.- As will be ap parent from Fig. d, bus bar supports iid are Serting locking wires 8d and t6 to hold the plates vrelative to the insulating plates t0 and t2.' The located between successive pairs ot dies or switch' fingers dit, andare supported by a pair oi rods M2 which extend the length or the manual and are threaded through complementary holes in the...

bus bar supports il@ and in the vertical plates itl. The bus bar supports il@ are suitably spaced by the notched strip it, thisstrip having notches-to y engage the bus bar supports as well as notches for engagement withthe vertical plates lil. The bus bar supports Vl i@ are provided with generally L-shaped openings I|4, the horizontal portions of which receive the insulating strips and the vertical portions of which receive bus bars H0. (It will be noted that the uppermost insulating strip 00 merely forms an upper limit stop for the switch finger and does not support la bus bar.)

'Ihe bus bars ||0 extend the full length of the manual and rest upon the insulating strips |00 and are guided for longitudinal movement in the vertical portions of the L-shaped slots I|4. The bus bars are preferably made of nickel alloy and have a wire I0 of palladium or other suitable metal welded or otherwise suitably secured thereto. In the preferred construction, the wire ||0 is spot welded to the bus bar H0 at short intervals along 4the length of the wire. This wire is preferably softer than the wires |06 used on the switch fingers in order that if wear takes place between them, the bus bar contact wire shall wear substantially to the exclusion of wear on the contact wires |06. y,

The switch. iingers 910 are iiexed so as to bring their contact wires |00 into electrical contact with the contact wires |00 of the bus bars I0 by means of actuators |20, which, as shown in Fig-2, are provided with apertures |22 through which the switch fingers 90 project. The actuators |20 abut shoulders |24 formed on the switch fingers 00 and are held against movement away from the shoulders |24 by a block |20 of insulating material which projects through apertures |20 formed in ali of the switch ngers 90 except the uppermost and lowerxnost fingers of a tier. The insulating block |20 thus rests upon the lowermost switch linger 00 and is held against removal by the uppermost of the switch fingers.

The upper ends of theactuators |20 are of reduced width, and project through suitable slots formed in the top sheet i0 of the switch compartment and through a thin sheet of felt |30 which is secured to the top sheet I0 by metallic strips |32 which may be riveted or otherwise suitably secured to the top sheet I0.

Inasmuch as the construction of the manual, that is, the construction of the keys and supports therefor, is more fully described and is claimed in my copending application, Serial No. 91,283, led July 18, 1936, the construction and operation of these parts will be but brieily described herein.'

Keys |34, |30 molded o! a suitable plastic composition-are secured to key stems in the form of metallic channels |30 which are supported on studs |40 and rest upon a fulcrum rod |42. The studs |4|0 are riveted to the horizontal leg portion of the angle strip i0 and at their upper ends are of reduced diameter and are threaded to receive adjusting nuts |44 by which the degree of compression of coil springs |40 which surround the studs |40 may be regulated. A grooved wooden strip |40 may be placed over the row of adjusting nuts |44 to prevent the accidental loosening thereof. v l A Each of the channels |30 has a felt pad |50 suitably secured thereto for providing a noiseless contact with the upper end of its associated actuator |20. Upward movement of the forward ends of the white keys |34 is Alimited by a felt strip |52 secured to the lower surface oi' the inwardly extending flange |54 of an angle strip |50 which is secured to the angle 24. The felt strip |52 is engaged by an integrally molded projection |50 formed at the forward end of each of the keys |04. Downward movement of the keys |04 is limited by a heavy felt pad |00 which rests upon and may be secured to the strip 04. Each oi' the black keys |30 is secured to the channel |00 by a pair of cap screws |02, |04 which are screwed into suitable threaded sockets molded into the body of the key |30. Both the white keys |34 and the black keys |00 are guided against lateral shifting movement by fabric pads |00 which are secured to the upwardly extending teeth |00 of a comb by U-shaped clips |12. The comb |10 has its horizontal flange portion |14 which is .longitudinally slidable relative to the bus bar sup ports i i0. As best shown in Figs. 4 and 5, the ends of the bus bars H6 are bent over and the ends clamped between a pair of insulating plates |80 and 88 by a pair of cap screws |00. I'he insulating plate |80 is riveted to one arm |92 of a bell crank lever |84 pivoted upon a pin |96 supported in a bracket |00. The bracket |90 may be secured to the leftmost vertical plate I0 by a pair of cap screws 200. The other arm 202 oi' the bell crank |94 has an open end slot in the form of a yokeembracing the reduced diameter portion 204 cfa spindle 200. ri'he spindle 200 has a threaded portion 200 screwed into an internally threaded block 2|0 supported by the leftmost vertical plate |0. The portion 200 is threaded into a kerfed shank 2|2, being secured against unscrewing by a pin 2|4 extending diametrically through the shank 2|2 and the threaded portion 200. The shank 2|2 extends through an aperture 2|6 formed in the rear sheet l2, a suitable washer 2i0 made of phenol condensation product `or similar material being held by a compression coil spring 22 in position to seal the opening 2| 0 against theadmission of dust. The inner end of the spring 220 abuts against a washer 222 which in turn abuts against the projecting ends of the pin 2|4. The spring 220 not only holds the wash- Aer 2|0 in place, but exerts a longitudinal pres- ,sure upon the threaded portion 200 of the spindle between a metallic channel 230 and the bottomk sheet I4 by the cap screw 40. 'I'he wires are then led over a fiber or other suitable insulating sheet 232, which is held in spaced position by a tube 234 of insulating material. Ametallic chan- 'nel 230 is clamped to the bottom sheet I4 by cap screws 50, and this channel, as well asthe two arms of the channel 200, carry notched combs 230, 240, and .242 of insulating material. vT'he wires 224 in addition to forming van electrical connection between the switch fingers 00 and the generators form an important part of the electrical'circuit of the instrument by providing a predetermined high impedance path for the ow of thecurrent from the generators to the output circuit. To obtainthe predetermined resistance in the wires224, they are measured to a certain length (approximately a yard long). lli. means were not provided to mount these hundreds of long wires, they would become tangled and snarled and the combs 238, 240, and 242 are therefore provided as a means to support the excess length of the insulated resistance wires 22d. As will be noted from Fig. 6, oneend of each of the resistance wires 22d is soldered to a soldering lug 2M, a plurality of -which are riveted to an insulating strip 246 riveted to the channel 226i. The intermediate length of wire is strung back and forth between the appropriate slots in the combs 23B, 2li@ and 2d?! so that the wire will be taut throughout its length. It will be understood that a, plurality of wires 226| will be connected to one of the soldering lugs 2M and that these wires, although of the same length, must be connected to different tiers of switch ngers. Wires 25tconnct the soldering lugs 2M to the generators. (The 'particular connections necessary are fully disclosed in the above mentioned Patent No. 1,956,350.) The wires 22d strung upon the combs 233, Mil and M2 are covered by a horizontal extension 2M of the rear sheet |12, the horizontal extension being secured to the bottom sheet |it by screws 250 threaded in suitable spacing studs 252.

It is believed that the operation of the key switches will have been apparent from the preceding detailed description of their construction. Briefly, upon depression of one of the keys Wd or |36, the channel stemk mt thereof will, in swinging downwardly, engage the upper 'end of the associated actuator |20. The'actuator will thereupon flex downwardly all of the switch fingers t0 of a vertical tier or file until the contact wires |06 of the switch fingers are rmly pressed against the contact wires ||8 of the bus bars Ht, completing the circuit from the generators (which are connected by wires 254 to the soldering lugs 244) to the output circuit which is connected -to the bus bars i6. Upon release of pressure upon the depressed key, the compression spring |86 will swing the forward end of the key upwardly, whereupon the switch fingers 90 will, `due to their resiliency, resume the position in which they are shown in Fig. 1, where their tip portions |04 are arrested by engagement with the insulating strips |00.

If, after a long period of use, some of the switches should fail to make contact, the-portion of the contact wires |8 which is engaged with the contact wire |06 on the switch ngers; may be shifted so as no longer to be in'registry with the contact wires |06. This is accomplished by turning the shank 2|2 of the spindle 206 and thus through the bell crank |94 pushing or pulling the bus bars ||6 in one direction or the other. Inasmuch as the contact wires |06 are of exceedinglysmall diameter, a slight longitudinal movement of the bus bars will result in bringing new portions of the bus contact wires ||8 in registry with the contacts |06 of the switch fingers. Since the contact wires |04 flex as their contacts |06 This wiping action results, however, in slight mechanical wear of the bus contact wire Md since it is softer than the contact wire |06 and it is for this reason that the-latter wire may, if desired, be made ofv slightly greater diameter than apea'ace the contact wire m6. By substantially concentrating any mechanical wearing of the contact wires upon the bus contact wire ||8, it is possible easily to` compensate for such wear by shifting the bus bars.

In the event that one of the switch contacts becomes defective due to the adhesionv of a parf ticle of lint or dust, such particles may usually tact, and while holding the key depressed shifting the bus bars back and `forth by rotation of the spindle shank 2|2. If desiredall of the switch contacts may be simultaneously cleaned by holding all of the keys depressed and shifting the bus bars back and forth.

From the above description, it will be noted that the manual and the key switches form a unit which is electrically connected to the instrument by many 'less wires than there are separate key-actuated switch circuits. Thus in the event of damage to the manual of an instrument, it may be easily removed for repair or replacement. Furthermore, this construction lends itself very advantageously to production of the instrument in large quantities at low cost.

It will be noted that the assembly of the switch ngers in their supporting-plates 80 and 82 and their connection with the actuator |20 is easily accomplished, since it is necessary merely to slide these iingers through the apertures 88 in the plates B0 and 82 and through the apertures |22 in the actuators |20 and to drop the insulating block |26 in position just prior to inserting the uppermost of a tier of switch iingers 90. M c

'I'he construction is such that although there are several hundred: switches, the assembly of them is very compact, with thev result that the switches of each tier may be located directly beneath, or in the plane of, the-key used to actuate them, and despite the large number of switches required, the cost of the switch assembly' is relatively small.

While I have shown and described a preferred embodiment of my invention, it will be readily understood by those skilled in the lart that variations may be made in the constructiondisclosed without departing from the basic features of my invention. I therefore do not wish to belim-v each in substantial alignment with its associated key, a plurality of bus bars extending in a direction perpendicular to the planes of said banks of switchv fingers and each bus bar being 1ocated in a position to be contacted by one of the switch iingers of each bank, and an actuator for each bank of said switch-fingers operable by the associated key to move the switch iingers into engagement with said bus barsrespectively.

2. In. an electrical musical instrument, the combination of a manual composed of a plurality of keys, a bank of switch ngers for each key, said banks of switch fingers being arranged in planes each in substantial alignment with its associated key, a plurality of bus bars extending in a direction perpendicular to the planes of said banks of switch ngers and each bus bar being located in a position to have a portion thereof contacted by one of the switch fingers of each bank, actuators individual to each bank of said switch fingers and operable by said keys respectively, and manually operable means to simultaneously shift all oi said bus bars longitudinally thereby to bring diierent portions thereof into position to be contacted by said switch ngers.

3. In an electrical musical instrument, the combination of a manual composed of a plurality of keys, a bank of switch fingers for each key, said banks of switch fingers being arranged in planes each in substantial alignment with its associated key, a plurality of bus bars extending in a direction perpendicular to the planes of said banks switch fingers and each bus bar being located in a position 'to be contacted by one of the switch iingers of each bank, an actuator for each bank of said switch ilngers operable by the associated key to move the switch iingers into engagement with said bus bars respectively, and means vto shift said bus bars lon- -gitudinally- 4. In an electrical xuusicai instrument, the combination of a plurality of conductors, each connected to a source of alternating current, keyoperated switches for selectively connecting said conductors tc an output circuit, a. housing for said switches, resistance 'wires connecting said conductors with said switches, and a plurality of combs mounted on said housing and forming supports for Stringing said wires.

5. In a multiple switch, a pair of spaced plates of insulating material having similar rows and illes of periorations formed therein, a pluralityY of movable switch ilngers extending through said perforations and each having a `part engaging one of said plates detachably to hold the switch iinger against longitudinal movement with respect to said plates, fixed contacts for said switch fingers, and an actuator having parts engaging each of the switch ilngers of a le and operable to iex the latter into contact with said xed contacts.

6. In an electrical musical instrument, the combination of a plurality of conductors, each connected to a source of alternating current, keyoperated switches for selectively connecting said conductors to an output circuit, relatively long Wires of predetermined impedance connecting said conductors with said switches, and a plurality of notched insulating strips xed-with respect to said switches and forming supports for Stringing said Wires.

7. A switch finger comprising a thin strip o! resilient metal having a latching part cooperable with a support detachably to hold the nger against longitudinalmovement relative to the support.

8. In an electrical musical instrument the combination of a plurality oi' similar tiers of switch fingers located in a row, a plurality of perforated bus bar supports of insulating material, a plurality of bus bars mounted for sliding movement through the perforations in said supports and located inv positions to be contacted by said switch merk, an insulating strip located beneath each oi said bus` bars` and forming al limit stop for said gers, to move a tier 'or switch fingersk han 'engagement with lingers from engagement with said insulating strips into contact with said bus bars respectively.

l0. A switch for electrical currents of low voltage and amperage comprising a movable switch :finger having a short length of contact wire secured thereto, and a second relatively nxed conm tact wire extending at an appreciable angle with respect to said iirst named contact wire and co-l operable therewith Ato complete an electrical circuit, said wires being in the order oi' .067 inch in diameter.

il. A switch for electrical currents of low voltage and amperage comprising a movable switch ilnger having a short length of contact wire secured thereto, a second relatively iixed contact wire extending at an appreciable angle with respect to said first named contact wire and cooperable therewith to complete an electrical circuit, said wires being in the order of .O07 inch in diameter, and means to shift one of said contact wires longitudinally to bring a dlerent portion lhereof into cooperable contacting relationship with the other of said wires.

l2. In a multiple switch assembly, the combination of a plurality of spaced switch finger supporting plates each having a plurality of periorations therein substantially aligned with the perforations in the other, switch iingersvhaving apertures and shoulders and extending through aligned periorations in said supporting plates, cooperating means on said iingers and one of said plates for holding said ilngers against longitudinal movement with respect to said plates, an actuator embracing a plurality of said lingers and abutting the shoulders thereon, and a block of insulating material extending through the per- !orations in said ilngers and operable to prevent appreciable movement of said actuator in a direction away from the shoulders on said fingers.

13. In an electrical musical instrument, a unitary manual and switch assembly, comprising a plurality of keys, a plurality of switches operable by said keys, terminals mounted on said assembly for connection to dierent electrical generators, and a plurality of wires each having one end connected to one of said terminals and their other ends connected to diilerent ones of said switches, whereby the assembly may be disconnected from said generators without disconnecting said wires.v

14. In an electrical musical instrument, the combination of a manual assembly comprising a plurality of keys, a plurality of switches associated with and operable by each key, a plurality of terminals mounted on said manual assembly, and a plurality of wires connecting said switches with said terminals, there being only one of said wires connected at one end to eachv of said switches, and a plurality of said wires connected at their other ends to a singlev one oi said terminals, wherebyconnection of a singleconductor to one oi' saidterminals'may be eilective to sup- 'pb canut to a plurality oi' said switches.

i5'. A vswitch assembly for electrical currents of low voltage and amperage comprising a plurality of movable switch members, each having a short length of contact wire secured thereto,

a bus element common to a pluralityV of said plete electrical circuits, and means to shift said bus element with respect to said switch members thereby to make possible the cleaning ofsaid contact Wires by a rubbing action.

16. In an electrical musical instrument the combination of a plurality of switches each comprising a pair of cooperable contacts, one of the contacts being normally stationary and the other movable'into engagement therewith, and means for simultaneously vmoving the normally stationary one of each pair of said contacts with respect to the other or the pair, thereby to clean the contacts by a rubbing action or to cause one of the contacts of each pair to engage the other at a point spaced from the original point of contact.

17. lin ay multiple switch assembly for currents of low voltage and amperage, a row of switch members, a bus bar of a base metal positioned adjacent said members, a contact wire oi a precious accenna of low voltage and amperage, a row of switchv members, each having a contact wire of precious lcontact metal secured thereto, a bus bar of a base metal positioned adjacent said members, a contactwire of precious metal secured to said bus bar in electrical conducting relationship therewith and extending at an appreciable angle with respect to the contact wires of said switch members, means selectively to move the contact wires oi said switch members into contact with the contact wire of said bus bar, and a manually operable means to shift said bus bar with respect to said switch members to change the points of contact between its contact wire and the contact wires of said switch members.

l9.`As an article of manufacture, a switch finger comprising a thin strip of resilient metal having a Support-'engaging notch formed in a side edge adjacent one end thereof and having a slot extending longitudinally of the strip at said end, whereby the portion of the strip near said notch will easily flex to permit disengagement of the notch from a support'. t

nAUnnNs Harmonia. 

